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Electronics and Communication Engineering - Analog Electronics

Exercise : Analog Electronics - Section 4
41.
An amplifier has open loop gain of 100, input impedance 1 kΩ and output impedance 100 Ω. If negative feedback with β = 0.99 is used, the new input and output impedances are
10 Ω and 1 Ω
10 Ω and 10 kΩ
100 kΩ and 1 Ω
100 kΩ and 10 Ω
Answer: Option
Explanation:

Input impedance with feedback = (1 kΩ) (1 + 100 + 0.99) = 100 kΩ. Output impedance with feedback = .

42.
In a BJT amplifier the power gain from base to collector is 4000. The power gain in dB is
3.6
36
7.2
72
Answer: Option
Explanation:

Gain in dB = 10 log (4000).

43.
In figure, secondary winding has 40 turns. For maximum power transformer to 2 ohm resistance the number of turns in primary is
20
40
80
160
Answer: Option
Explanation:

.

44.
In a CE amplifier circuit the dc voltage between emitter and ground
is always zero
cannot be zero
may or may not be zero
is negative
Answer: Option
Explanation:

Since dc is flowing through emitter resistance, dc voltage cannot be zero.

45.
A buffer amplifier should have
high output impedance and high input impedance
high output impedance and low input impedance
low output impedance an low input impedance
low output impedance and high input impedance
Answer: Option
Explanation:

So that it can couple high impedance source to low impedance load and maximum power can be transferred.

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